Three miles east of the Cormorant oilfield|North Cormorant oil field
in the North Sea, the crew on board the drill rig ''Venture One'' was preparing to lower a Blow Out Preventer
(BOP) to the seabed 510 feet below. It was 10 May 1977,
and International Underwater Contractors (IUC) diving supervisor Richard Pettit had been asked to inspect the Permanent Guide Base to verify that it was clear of any obstructions that might prevent the installation of the BOP.